Scroll intake for rotary power conversion machines



March 7, 1967 J. A. RYLATT 3,307,587

SCROLL INTAKE FOR ROTARY POWER CONVERSION MACHINES Filed July 28, 1964 2 Sheets-Sheet l m! ss 23 21a. I 11 20 l I 14 Q: f 34 INVENTOR JOHN ANTHONY RYLATT ATTORNEYS March 7, 1967 J. A. RYLATT 3,307,587

SCROLL INTAKE FOR ROTARY POWER CONVERSION MACHINES Filed July 28, 1964 v 2 Sheets-Sheet 2 11 I F|G.2

'INVENTOR JOH N ANTHONY RYLATT ev v Xfa;

ATTO RN EYS United States Patent (3 "3,307,587 SCROLL INTAKE FOR ROTARY POWER ooNvEnsroN aonmns Inhn Anthony kylatt, Acton, Ontario, Canada, assignor This invention relates to intake volutes for rotary compressors, turbines and the like.

Scroll or volute intakes are required in many installations, including turbines, rotary compressors and other rotary power conversion machines, particularly where the working fluid must be turned through a right-angled bend and then fed to an annulus. Conventional scroll ducts usually appear as a singly convoluted passage of curvilinear and sometimes rectilinear cross-section diminishing in size to infinite smallness.

It will be recognized that such a structure in association with an annular outlet can give rise to uneven flow conditions in the region of the small end of the passage. It is also an established fact that gas flow into any inlet whose edges are flush with a surface is not as efficient, from a fluid flow standpoint, as an inlet having lips which extend above the surface. In a scroll passage diminishing .to infinite smallness, the provision of an annular outlet having an unbroken raised lip or lips extending into the passage becomes diflicult if not impossible. Unless extreme care is taken with the design, stagnant or reverse flow conditions may arise in the transition or scroll passages and irregularities in the passage walls may cause flow fluctations.

Manufacturing methods for volute ducts fall generally into two classes: casting and sheet metal fabrication. Design considerations, the type of working fluid and the conditions under which it is operating are important in determining the manufacturing method adopted. From a manufacturing standpoint, the design of the present invention offers considerable advantages where sheet metal construction is the manufacturing method used.

Whereas known methods of scroll fabrication in sheet metal require highly skilled work and accurately made forms, dies and assembly jigs, the present invention contemplates a scroll duct fabricated from components which, with the exception of the transition portion, are all in the form of surfaces of revolution. The scroll, therefore, is easy to design and to manufacture requiring only simple assembly jigs. Moreover since the design, as will be described hereinafter, is adapted to damp out fluctuations in flow due to irregularities in the scroll duct, manufacturing tolerances need not be held so close as heretofore. As regards its operation, because the scroll duct has a constant mean radius and a constant flow area, flow conditions at the outlet are predictable at all operating levels. Gas velocity is constant and kept to a minimum and thus pressure losses are kept to a minimum.

A further important advantage of the invention lies in the convenience with which the transition portion is mated with the scroll portion. In many scroll duct designs there is considerable interference between the tailend of the scroll passage and the transition, which results in a reduction in the initial flow area. With the present design there is only minor interference at this point causing only a very small reduction in initial flow area which is more than compensated for by the otherwise excellent flow characteristics exhibited by the scroll duct.

The primary object of this invention is the provision of a design for a scroll duct of sheet metal which has superior gas flow characteristics.

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Other objects and advantages will be apparent to t hose skilled in the art from the follovw'ng description taken in conjunction'with the accompanying drawings wherein like characters refer to like parts throughout the several views and in which:

FIG. 1 is an exploded perspective view of the components of a scroll duct;

FIG. 2 is a perspective broken-away view of an assembled scroll duct;

FIG. 3 is a perspective broken-away view of an assemble-d duct taken from a viewpoint 180 angularly distant from the viewpoint for FIG. 2;

FIG. 4 is a partial sectional view of a scroll duct showing an alternate construction for one portion of the duct; and

FIG. 5 is a partial sectional view of a scroll duct showing a further construction for the duct portion shown in FIG. 4.

In FIG. 1, a scroll duct is generally indicated by the numeral 10, and comprises an outer cylindrical wall 11, an inner cylindrical wall 12 concentric with the outer wall 11, a helicoidal top wall 13 bridging between the outer 11 and inner 12 walls, and an annular radial bottom wall 14 of cross-section similar to that of the top wall 13, the bottom wall 14 being oriented transversely to the common axis of the outer 11 and inner 12 walls and extending from the outer wall 11 inwardly towards but terminating short of the inner wall 12 thus leaving an annular outlet passage between the bottom wall 14 and the inner wall 12. The helicoidal top wall 13 coils upwardly through 360 from a lower extremity 15 spaced above the bottom wall 14 to an upper extremity 16 spaced above the lower extremity 15. A shallow annular wall 17 of frusto-conical configuration is adapted to be fixed medially and apex downwardly to the inner margin of the bottom wall 14, and thus defines, with the inner wall 12, an annular outlet passage 18 (FIGS. 2 and 3). A transition duct shown generally at 19 provides a smooth entry into the scroll duct.

The outer wall ill is formed from a rectilinear sheet of metal and has a lower edge 20, parallel opposed side edges 21 and 21a perpendicular to the edge 20, and an edge 22, opposed to edge 20 and angled at the chosen pitch of the helicoidal top wall 13. The sheet is formed into an open-ended cylinder, the edges 21 and 21a abut-i ting and joined in any suitable manner such as welding, and such that the edge 20 becomes a continuous edge in a plane normal to the longitudinal axis of thecylinder and edge 22 forms a 360 helix so that a portion of edge 21a remains exposed.

The inner wall 12 is formed in a like manner to outer wall 11 with a lower edge 23, parallel opposed side edges 24 and 25 perpendicular to the edge 23 and an upper edge 26 angled at the same pitch as upper edge 22 of wall 11. The metal blank is formed into a cylinder and the edges 24 and 25 are butt-welded so that the edge 23 be comes a continuous edge and so that the edge 26 forms a helix of the same pitch as the helix formed by the edge 22 of the outer wall 11. A portion of the edge 25 is thus left exposed.

The helicoidal top wall 13 is formed from an annular sheet metal blank appropriately dimensioned. It is spun or otherwise formed into a shallow arcuate or dished cross-section with the outer and inner edges turned in the direction of curvature to provide narrow parallel flanges 27 and 28 respectively (FIG. 1). After forming as just described the blank is cut along a radius line. The ends or extremities 15 and 16 so formed are sprung apart so that the blank takes on the required helicoidal shape.

The outer and inner walls 11 and 12 are held in coaxial relationship in a simple jig, the exposed portions of edges 21a and 25 being in radial alignment. The end wall 13 is then placed between the outer and inner walls so that flanges 27 and 28 are adjacent to edges 22 and 26 respectively, and so that the upper extremity 16 is aligned with the edges 21a and 25 of the outer and inner walls 11 and 12. The end wall 13 is then clamped and welded in position in known manner.

The bottom wall 14 is formed, in a similar manner to Wall 13, from an annular blank having an outer diameter equal to that of the upper wall 13 and an inner diameter greater than that of the wall 13. The arcuate curve formed in the blank is similar to that of the wall 13. The outer edge of the bottom wall 14 is turned in the direction of curvature of the arc to form a narrow flange 33 while the inner edge is turned in the opposite sense to form a narrow flange 34 substantially parallel to flange 33. Flange 34 abuts an outer surface of the shallow annular wall 17 at 35. Again, with the aid of a very simple jig, the walls 14 and 17 may be welded together. The bottom wall 14 is then placed into the open end of the scroll duct so that the flange 33 lies adjacent to the edge '20 of outer wall 11 and the seam thus formed is welded all around. It can now be seen how the annular wall 17 is supported in spaced relation to and coaxially with the inner wall 12 to define the annular outlet passage 18. As may be clearly seen in FIGS. 2 and 3, the annular wall 17 extends some distance above the inner surface of the bottom wall 14, terminating in a rolled lip 37. The portion of the scroll duct lying between the bottom Wall 14 and rolled lip 37 defines an annular chamber 38 which serves to damp out fluctuations in gas flow due to any irregularities in the duct walls.

As shown in FIGS. 4 and 5, the structure defining the annular outlet passage 18 may be modified so as to lie at any radial station between the outer wall 11 and the inner wall 12. In FIG. 4 the bottom wall 39 extends from the inner wall 12 outwardly towards but terminating short of the outer wall 11. A slightly ogival frustoconical annular wall 40 is fixed medially and apex upwardly to the outer margin of the bottom wall 39. There is thus created an annular outlet passage 41 between the frusto-conical annular wall 40 and the outer wall 11.

In FIG. are shown a first annular bottom wall portion 42 and a second annular bottom wall portion 43. The first portion 42 extending from the outer wall 11 inwardly and the second portion 43 extending from the inner wall 12 outwardly. There is an annular passage 44 defined between the first 42 and second 43 portions. A slightly ogival frusto-conical annular wall 45 is fixed medially and apex upwardly to the outer margin of the second portion 43, and a slightly flaring frusto-conical annular wall 46 is fixed medially and apex downwardly to the inner margin of the first portion 42. The two frusto-conical annular walls 45 and 46 are spaced from each other to form an annular outlet passage 47 from the scroll duct 10.

Each of the frusto-conical annular walls 40, 45 and 46 has its upper edge formed into a roll.

The remaining portion of the scroll is the transition duct way 19 which is designed to provide a smooth transition from the circularly curved passage within the rectangular opening formed between the edges 21a and 25 land the extremities 15 and 16, to a substantially rectilinear passage towards the outer end of the ductway. The preferred construction of the transition may be easily followed by reference to FIG. 1.

A barb-shaped plate 49 has a curved inner edge 50 which is welded adjacent to the edge 22 of the outer wall 11. An outer edge 51 of the plate 49 is contoured to the desired curve of the transition ductway and provided with a narrow flange 52, while edge 53 defines the outer limit of the duct remote from the volute. A rectilinear wall plate 55 suitably dimensioned is welded to the edge 21a and the flange 52. Similarly, a wall plate 56 suitably dimensioned is welded to the edge 25 and also has an edge 57 contoured to the arcuate upper surface of the wall 13 which it traverses obliquely and to which it is welded as at 58 (FIG. 3). An upper wall 59 having narrow edge flanges 60 and 61 and being formed to the entry curve of the transition is welded to the adjacent upper edges of the walls 55 and 56 and to the edge 16 of the end wall 13 as a continuation of the wall 13 to complete the transition duct.

Regarding the edge joining of the component parts of the scroll, although the preferred embodiment employs lapped flange and butt-welds it will be realized that other forms of edge joint common in the sheet metal fabrication art, such as crimping, rolling and rivetting, may be used as desired.

It will be appreciated that it is not essential to the functioning of this invention that the top wall 13 cover exactly 360. It would be possible, by adding an extension piece at either the upper or lower extremity of the top wall 13, to extend the wall 13 to cover an angle greater than 360. Such an extension could, within limits,

be made without danger of adversely aflecting the operation of the invention. Likewise, the wall 13 could be cut to cover an angle less than 360 although the angle should not drop much below 345. Using an angle of less than 360, the transition ductway 19 could be arranged to slope downwardly from above into the opening defined between the outer wall 11, the inner wall 12 and the top wall 13, the opening in this case being four-sided, but not rectangular.

What I claim as my invention is:

1. A scroll duct capable of fabrication from sheet metal elements in the form of surfaces of revolution for rotary power conversion machines comprising, cylindrical concentric outer and inner walls, annular bottom wall means oriented transversely to the common axis of the outer and inner walls and extending bet-ween the outer wall and the inner wall, the bottom wall means being interrupted by an annular passage, a helicoidal top wall bridging between the outer and inner walls and coiling upwardly from a lower extremity spaced above the bottom wall to an upper extremity, there being thus a foursided opening into the scroll duct defined between the outer, inner and top walls.

2. A scroll duct capable of fabrication from sheet metal elements in the form of surfaces of revolution for rotary power conversion machines comprising, cylindrical concentric outer and inner walls, an annular bottom wall oriented transversely to the common axis of the outer and inner walls and extending from the outer wall in'wardly towards but terminating short of the inner wall thus leaving an annular passage between the bottom wall and the inner wall, a helicoidal top wall bridging between the outer and inner walls and coiling upwardly through substantially 360 from a lower extremity spaced above the bottom wall to an upper extremity, there being thus a four-sided opening into the scroll duct defined between the outer, inner and top walls.

3. A scroll duct as claimed in claim 2 in which a slightly flaring frusto-conical annular wall is fixed medially and apex downwardly to the inner margin of the bottom wall, the upper edge of the frusto-conical wall forming a rolled lip, there being thus formed an annular outlet passage between said frusto-conical annular wall and the inner wall.

4. A scroll duct capable of fabrication from sheet metal elements in the form of surfaces of revolution for rotary power conversion machines comprising, cylindrical concentric outer and inner walls, an annular bottom wall oriented transversely to the common axis of the outer and inner walls and extending from the inner wall outwardly towards but terminating short of the outer wall thus leaving an annular passage between the bottom wall and the outer wall, a helicoidal top wall bridging between the outer and inner walls and coiling upwardly through substantially 360 from a lower extremity spaced above the bottom wall to an upper extremity, there being thus a four-sided opening into the scroll dluct defined between the outer, inner and top walls.

5. A scroll duct, as claimed in claim 4, in which a slightly ogival frusto-conical annular wall is fixed medially and apex upwardly to the outer margin of the bottom wall, the upper edge of the frusto-conieal wall forming a rolled lip, there being thus formed an annular outlet passage between said frusto-conical annular wall and the outer wall.

6. A scroll duct capable of fabrication from sheet metal elements in the form of surfaces of revolution for rotary power conversion machines comprising, cylindrical concentric outer and inner walls, a first and a second annular bottom wall portion oriented transversely to the common axis of the outer and inner walls, the first portion extending from the outer wall inwardly and the second portion extending from the inner wall outwardly, there being an annular passage defined between the first and the second portion, a helicoidal top wall bridging between the outer and inner walls and coiling upwardly through substantially 360 from a lower extremity spaced above the bottom Wall to an upper extremity, there being thus a four-sided opening into the scroll duct defined between the outer, inner and top walls.

7 A scroll duct as claimed in claim 6, in which a slightly ogival frusto-conical annular wall is fixed medially and apex upwardly to the outer margin of the second bottom wall portion, and in which a slightly flaring frusto-conical annular wall is fixed medially and apex down wardly to the inner margin of the first bottom wall portion, the upper edge of each frusto-conical annular wall forming a rolled lip, there being thus formed an annular outlet passage between the two frusto-conical annular walls.

8. A scroll dluct as claimed in claim 1 in which a duct- Way of substantially rectangular cross-section leads from the four-sided opening to a point beyond the outer cylindrical 'wall, the duct-way being shaped to provide a smooth transition from the circularly curved passage within the four-sided opening to a substantialy rectilinear passage towards the outer end of the ductway.

9. A scroll duct as claimed in claim 1 in which the bottom wall is slightly downwardly dished, and the upper helicoidal Wall is slightly upwardly dished.

References Cited by the Examiner UNITED STATES PATENTS 2,642,895 6/1953 Bertin et a1 138-37 LAVEJRNE D. G'EIGEJR, Primary Examiner.

T. L MOOQRHEAD, Assistant Examiner. 

2. A SCROLL DUCT CAPABLE OF FABRICATION FROM SHEET METAL ELEMENTS IN THE FORM OF SURFACES OF REVOLUTION FOR ROTARY POWER CONVERSION MACHINES COMPRISING, CYLINDRICAL CONCENTRIC OUTER AND INNER WALLS, AN ANNULAR BOTTOM WALL ORIENTED TRANSVERSELY TO THE COMMON AXIS OF THE OUTER AND INNER WALLS AND EXTENDING FROM THE OUTER WALL INWARDLY TOWARDS BUT TERMINATING SHORT OF THE INNER WALL THUS LEAVING AN ANNULAR PASSAGE BETWEEN THE BOTTOM WALL AND THE INNER WALL, A HELICOIDAL TOP WALL BRIDGING BETWEEN THE OUTER AND INNER WALLS AND COILING UPWARDLY THROUGH SUBSTANTIALLY 360* FROM A LOWER EXTREMITY SPACED ABOVE THE BOTTOM WALL TO AN UPPER EXTREMITY, THERE BEING THUS A FOUR-SIDED OPENING INTO THE SCROLL DUCT DEFINED BETWEEN THE OUTER, INNER AND TOP WALLS. 